Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/004—Details
  • H01G9/022—Electrolytes; Absorbents
  • H01G9/025—Solid electrolytes
  • H01G9/028—Organic semiconducting electrolytes, e.g. TCNQ
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
  • H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
  • H01G9/15—Solid electrolytic capacitors

Definitions

• This disclosure relates to solid electrolytic capacitor elements and solid electrolytic capacitors.
• a solid electrolytic capacitor comprises a solid electrolytic capacitor element, a resin exterior body or case that seals the solid electrolytic capacitor element, and an external electrode that is electrically connected to the solid electrolytic capacitor element.
• the solid electrolytic capacitor element comprises, for example, an anode body, a dielectric layer formed on the surface of the anode body, and a cathode portion that covers at least a portion of the dielectric layer.
• the cathode portion includes a conductive polymer (e.g., a conjugated polymer and a dopant) that covers at least a portion of the dielectric layer.
• the conductive polymer is also referred to as a solid electrolyte.
• Patent Document 1 proposes a method for manufacturing an electrolytic capacitor, which includes a step of impregnating an anode body having a dielectric film formed on its surface with a first dispersion solution containing particles of a first conductive polymer and a first solvent, and then impregnating the anode body with a second dispersion solution containing particles of a second conductive polymer and a second solvent, the pH of the first dispersion solution being closer to 7 than the pH of the second dispersion solution.
• Patent Document 2 proposes a conductive polymer composite which is made of PEDOT (poly(3,4-ethylenedioxythiophene)) and a polyanion, and has a conductive potential ⁇ of -0.23 or more, calculated by the following formula ( I), where I1 is the peak intensity at 1260 cm -1 in the Raman spectrum, I2 is the peak intensity at 1420 cm-1 , A1 is the absorbance at a wavelength of 950 nm in the optical absorption spectrum, and A2 is the absorbance at a wavelength of 2300 nm.
• PEDOT poly(3,4-ethylenedioxythiophene)
• the first aspect of the present disclosure relates to a solid electrolytic capacitor element.
• the solid electrolytic capacitor element includes an anode body including a porous portion at least on the surface, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte covering at least a portion of the dielectric layer.
• the anode body includes elemental tantalum, and the solid electrolyte includes elemental sulfur.
• the solid electrolyte has a first portion disposed within the voids of the porous portion, and a second portion disposed outside the porous portion from a main surface of the anode body having the dielectric layer.
• the abundance ratio of the sulfur element is 0.17% or more when the abundance ratio of the tantalum element is taken as 100%.
• the second aspect of the present disclosure relates to a solid electrolytic capacitor that includes at least one of the solid electrolytic capacitor elements described above.
• ESR equivalent series resistance
• FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to an embodiment of the present disclosure.
• the surface layer of the anode body is formed with a porous portion having fine voids.
• the liquid dispersion contains particulate conductive polymers in which a polymer dopant (such as a polymer anion) is composited with a conjugated polymer. Therefore, when a solid electrolyte is formed using the dispersion, it is difficult for the particulate conductive polymer to fill deep into the fine voids, making it difficult to increase the filling rate of the conductive polymer in the porous portion. In this case, the equivalent series resistance (ESR) of the solid electrolytic capacitor is likely to fluctuate significantly when exposed to high temperatures.
• ESR equivalent series resistance
• the method of forming a solid electrolyte using a liquid dispersion is simple and has become the mainstream method of forming a solid electrolyte in recent years.
• a solid electrolytic capacitor element at least the surface layer of the anode body has a porous portion with fine voids.
• the dielectric layer is formed along the inner wall surface of the depression (sometimes called a pit) on the surface of the anode body, including the inner wall surface of the voids in the porous portion. Therefore, the surface of the dielectric layer has fine irregularities according to the shape of the surface of the anode body.
• the liquid dispersion contains particulate conductive polymers (such as conjugated polymers and dopants) with relatively high molecular weights.
• a high molecular weight polymer anion is preferably used as the dopant from the viewpoint of high affinity for conjugated polymers and easy to ensure high stability and high heat resistance.
• the ESR tends to be high. This is presumably due to the following reasons. Although the conductive polymer particles contained in the liquid dispersion fill the vicinity of the openings of the minute recesses on the surface of the dielectric layer in the porous portion, they do not penetrate deep into the porous portion, making it difficult to increase the filling rate of the conductive polymer. This increases the resistance between the dielectric layer and the solid electrolyte, and the initial ESR tends to be high. In addition, when the filling rate of the conductive polymer in the porous portion is low, the voids tend to become air passages.
• the conductive polymer deteriorates due to oxidation degradation of the conjugated polymer or dedoping of the dopant due to decomposition, etc., due to the action of moisture or oxygen contained in the air, and the conductivity of the conductive polymer decreases. Such deterioration of the conductive polymer is particularly noticeable in high temperature environments or high temperature and high humidity environments.
• the volume of the conductive polymer changes in high temperature environments or high temperature and high humidity environments. The movement of the first portion held within the gap is restricted by the metal skeleton of the porous portion, while the second portion is prone to movement due to volume changes in high temperature or high temperature/high humidity environments, and distortion is likely to occur between the first and second portions.
• Such distortion causes cracks to form between the surface of the first portion or the porous portion and the second portion, reducing the number of contact points. This is thought to increase the resistance between the first portion or the porous portion and the second portion. As a result, it is thought that the ESR fluctuates significantly when the solid electrolytic capacitor is exposed to high temperature or high temperature/high humidity environments.
• a method for forming a solid electrolyte other than the method using a liquid dispersion there is also a method of forming a solid electrolyte by using in situ polymerization, such as chemical polymerization on the surface of an anode body having a dielectric layer.
• in situ polymerization it is difficult to control the polymerization reaction, and it is generally difficult to obtain a uniform solid electrolyte, and the types of raw material monomers and dopants for conjugated polymers that can be used are limited.
• pyrrole compounds are used in in situ polymerization, and low molecular weight compounds such as aromatic sulfonic acids are used as dopants.
• the stability of the dopants and conductive polymers is low, and dedoping or deterioration of the conductive polymer occurs easily, and the ESR is easily changed when exposed to high temperature or high temperature and high humidity environments.
• the solid electrolytic capacitor element of the present disclosure includes an anode body including a porous portion at least on the surface thereof, a dielectric layer covering at least a portion of the surface of the anode body, and a solid electrolyte covering at least a portion of the dielectric layer.
• the anode body includes tantalum element (Ta element), and the solid electrolyte includes sulfur element (S element).
• the solid electrolyte has a first portion disposed within the voids of the porous portion, and a second portion disposed from the main surface of the anode body having the dielectric layer to the outside of the porous portion.
• the abundance ratio of S element is 0.17% or more when the abundance ratio of Ta element is 100%.
• the solid electrolytic capacitor element may be simply referred to as a capacitor element.
• the abundance ratio of the S element is relatively large, at 0.17% or more, relative to the abundance ratio of the Ta element in the porous portion, thereby reducing the fluctuation of the ESR when the solid electrolytic capacitor is exposed to high temperatures.
• the S element is mainly derived from the conjugated polymer and dopant that constitute the solid electrolyte.
• the polythiophene-based conjugated polymer contains the S element in the thiophene ring
• the dopant contains the S element derived from an anionic group such as a sulfo group.
• the anode body containing the Ta element is mainly composed of Ta or a Ta alloy, and the dielectric layer is composed of a Ta oxide.
• the relatively large abundance ratio of the S element relative to the abundance ratio of the Ta element in the porous portion means that the ratio of the solid electrolyte contained in the porous portion is relatively large (in other words, the filling rate of the solid electrolyte in the voids of the porous portion is high).
• the abundance ratio of the S element in the porous portion is within the above range, and the relatively high filling rate of the solid electrolyte is obtained, and the number of air flow paths is reduced, thereby preventing the progression of deterioration of the solid electrolyte.
• the solid electrolyte is arranged in the voids of the porous portion at a high filling rate, it is believed that even if the volume of the solid electrolyte changes due to the solid electrolytic capacitor being exposed to a high temperature or high humidity environment, a relatively large number of contact points are maintained between the first portion or the porous portion and the second portion. Therefore, it is believed that the fluctuation in ESR when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment can be reduced.
• the relatively high S element content in the porous portion as described above can be obtained, for example, by the following method.
• a dielectric layer is formed on the surface of an anode body containing Ta element and a porous portion at least on the surface layer, and the anode body having the obtained dielectric layer on its surface is precoated, then immersed in a polymerization solution containing a precursor of a conjugated polymer and a polymer anion containing an S element, and electrolytically polymerized in a three-electrode system.
• the surface of the dielectric layer is covered with a conductive material at a certain coverage rate by the precoat process, and a precoat layer of the conductive material is formed.
• the precursor and the polymer anion are dissolved in the polymerization liquid, they easily penetrate deep into the fine voids of the porous part. Therefore, polymerization easily proceeds not only near the opening of the voids but also in the deep parts of the voids. Therefore, it is considered that a high filling rate of the solid electrolyte in the voids can be obtained.
• the polymerization of the precursor of the conjugated polymer proceeds while interacting with the polymer anion, and in addition, the high orientation of the formed conjugated polymer is easily obtained, and the polymer anion is relatively uniformly dispersed, and a relatively high doping rate is easily obtained.
• the conductivity of the solid electrolyte in the first part can be increased, and when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment, dedoping or deterioration of the conjugated polymer is unlikely to occur.
• the filling rate of the solid electrolyte in the porous part is high, even if the volume of the solid electrolyte changes when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment, the contact point between the first part or the porous part and the second part is maintained. Therefore, it is considered that the above-mentioned excellent effects can be obtained.
• the high filling rate of the solid electrolyte in the porous portion allows the resistance of the first portion to be kept low from the initial stage, and the initial ESR to be kept low.
• the low resistance of the first portion ensures a relatively high initial capacity.
• the abundance ratio of S elements in the porous portion is low. This is thought to be because, as described above, even when a liquid dispersion is used, the filling rate of the solid electrolyte in the porous portion is low. Also, even when there is no precoat treatment, or when the coverage rate of the precoat layer is low even after the precoat treatment, the abundance ratio of S elements in the porous portion is low, less than 0.17%.
• Three-electrode electropolymerization is carried out using three electrodes: an anode body with a dielectric layer formed on its surface, a counter electrode, and a reference electrode.
• a reference electrode allows precise control of the anode potential without being affected by changes in the natural potential of the counter electrode.
• the electropolymerization reaction is more precisely controlled than in the two-electrode type using an anode body and a counter electrode, and it is believed that the polymer chains grow slowly while interacting with the polymer anion.
• the orientation of the formed conjugated polymer is improved, and the dispersion of the polymer anion is improved, resulting in the formation of a more uniform and dense solid electrolyte.
• the high coverage of the precoat layer makes it easier for the polymerization reaction to proceed in the voids of the porous part. Therefore, it is believed that a more uniform and dense solid electrolyte is formed with a high filling rate in the voids of the porous part.
• the high dispersion of the polymer anion makes it easier to obtain a relatively high doping rate, and that it is easier to increase the conductivity of the solid electrolyte itself.
• the abundance ratio of the S element is, for example, 5% or less.
• EMA electron probe microanalyzer
• the ratio (%) of the net strength of the S element when the net strength of the Ta element is 100% is calculated.
• the ratio (%) of the net strength of the S element is calculated for multiple areas (e.g., five areas), the average value is calculated, and the ratio (%) of the S element when the ratio of the Ta element in the porous part is 100% is calculated.
• the analytical sample can be prepared, for example, by the following procedure. First, the solid electrolytic capacitor or capacitor element is embedded in a curable resin and the curable resin is cured.
• the anode body has a first end and a second end opposite to the first end, and the solid electrolyte is formed on the second end side of the anode body.
• the cured product obtained above is wet-polished or dry-polished so that a cross section perpendicular to the length direction of the capacitor element and parallel to the thickness direction is exposed.
• the exposed cross section is smoothed by ion milling.
• a platinum film having a thickness of 1 nm to 2 nm is formed by sputtering platinum (Pt) on the smoothed cross section using a sputtering device. In this way, the analytical sample is obtained.
• the cross section is a cross section at a position greater than 0 and not more than 0.05 from the end on the second end side of the region where the solid electrolyte is formed.
• the first portion may contain a first polymer component corresponding to a conjugated polymer and a second polymer component corresponding to a polymer anion containing a sulfur element.
• the first component contains these polymer components (particularly the second polymer component), it is difficult to increase the filling rate of the solid electrolyte in the first portion.
• the first portion is formed by a precoat process and a three-electrode electrolytic polymerization, so that even when the first portion contains the above-mentioned polymer components, the abundance ratio of the S element in the porous portion can be increased, and a high filling rate of the solid electrolyte can be ensured.
• the first polymer component may contain an S element.
• S elements present in the porous portion.
• it is easy to obtain higher electrical conductivity in the first portion.
• a ratio I p1 /I p2 of an intensity I p1 of a first peak specific to the first polymer component to an intensity I p2 of a second peak specific to the second polymer component may be equal to or greater than 2.
• the orientation and crystallinity of the conjugated polymer in the first portion are relatively high, it is easy to ensure high conductivity of the solid electrolyte.
• the ratio I p1 /I p2 may be equal to or less than 7. In this case, a relatively high doping rate is easily obtained, and higher conductivity of the solid electrolyte is obtained, which is advantageous in keeping the ESR low.
• the conjugated polymer in the first portion, may include a monomer unit corresponding to a thiophene compound.
• the polymer anion may include a monomer unit corresponding to an aromatic sulfonic acid compound.
• a first peak specific to the first polymer component may be observed in the range of 1200 cm -1 to 1600 cm -1 .
• a second peak specific to the second polymer component may be observed in the range of 800 cm -1 to 1100 cm -1 . In such a case, since high conductivity of the solid electrolyte is easily obtained in the first portion, it is advantageous in suppressing the ESR low.
• the weight-average molecular weight of the polymer anion may be 100 or more and 500,000 or less. Even if the weight-average molecular weight of the polymer anion is in this range, the solid electrolyte can be placed in the voids of the porous portion at a high filling rate by the precoat treatment and three-electrode electrolytic polymerization, making it easy to obtain high conductivity in the first portion. In addition, higher stability of the conductive polymer can be obtained. Therefore, the fluctuation of ESR when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment can be further reduced.
• the anode body may be a porous sintered body.
• the average depth of the pores in the porous portion is about several tens of ⁇ m.
• the average depth of the pores in the porous portion in an anode body having a dielectric layer is, for example, 100 ⁇ m or more, and usually 300 ⁇ m or more. Therefore, in the case of a porous sintered body, it is difficult to arrange a solid electrolyte in the porous portion at a high filling rate compared to the case of an anode foil.
• the solid electrolyte can be arranged in the porous portion at a high filling rate by the pre-coating process and the three-electrode electrolytic polymerization, so that high conductivity is obtained and the deterioration of the conductive polymer is suppressed by reducing the flow of air in the pores. Therefore, even when the anode body is a porous sintered body, the fluctuation of ESR when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment can be suppressed.
• the present disclosure also includes a solid electrolytic capacitor element that includes at least one capacitor element described in any one of (1) to (8) above.
• the capacitor element and solid electrolytic capacitor of the present disclosure are described in more detail, including the configurations (1) to (9) above. To the extent that there is no technical contradiction, at least one of the configurations (1) to (9) above may be combined with at least one of the elements described below.
• the capacitor element includes an anode portion and a cathode portion.
• the anode section includes an anode body.
• the anode section may include an anode body and an anode wire.
• the anode body includes Ta element. Ta functions as a valve metal.
• the anode body may include Ta metal, a Ta alloy, or both.
• the anode body has a porous portion at least on the surface.
• the porous portion of the anode body has many fine voids. Due to such porous portion, the anode body has a finely uneven shape.
• the anode body may be, for example, a porous molded body or a porous sintered body (such as a sintered body of a porous molded body) of particles containing Ta element. In these cases, the entire anode body is porous.
• Each of the porous molded body and the porous sintered body may be in a sheet shape, a rectangular parallelepiped, a cube, or a shape similar to these.
• An anode body having a porous portion on the surface layer can be obtained, for example, by roughening the surface of a substrate (such as a sheet-like (e.g., foil-like, plate-like) substrate) containing Ta element.
• the roughening may be performed, for example, by etching (electrolytic etching, chemical etching, etc.).
• Such an anode body has, for example, a porous portion formed integrally with the core on both the surface of the core and the surface of the core.
• a porous sintered body containing Ta element is preferable.
• the anode body may have an anode lead portion including a first end, and a cathode forming portion including a second end opposite the first end.
• a cathode portion including a solid electrolyte is formed on the surface of the cathode forming portion of the anode body.
• the anode lead portion is used, for example, for electrical connection with an external electrode on the anode side.
• An anode lead terminal may be connected to the anode lead portion.
• the anode part may include an anode wire.
• the anode wire may be a wire made of a metal. Examples of the material of the anode wire include valve metal, copper, and copper alloy. Examples of the valve metal include aluminum, tantalum, niobium, and titanium.
• a part of the anode wire is embedded in the anode body, and the remaining part protrudes outward from the end face of the anode body. The end of the anode wire protruding outward corresponds to the first end, and the end of the anode body opposite to the first end corresponds to the second end.
• the dielectric layer is formed so as to cover at least a part of the surface of the anode body (for example, at least a part of the surface of the porous portion).
• the dielectric layer is an insulating layer that functions as a dielectric.
• the dielectric layer is formed by anodizing tantalum (Ta) on the surface of the anode body.
• Ta tantalum
• the first part peels off from the second part and falls into the pores. This reduces the conductivity of the solid electrolyte.
• the deterioration of the solid electrolyte is particularly noticeable when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment. Therefore, in a solid electrolytic capacitor using an anode body that is entirely porous, such as a porous molded body or a porous sintered body (particularly a porous sintered body), the fluctuation of ESR is likely to be significant when exposed to high temperatures or high temperature and high humidity environments.
• the ratio of S elements in the porous portion can be increased, and the solid electrolyte can be placed in the pores at a high filling rate. This reduces the fluctuation in ESR when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment.
• the dielectric layer may be formed of a material that functions as a dielectric layer.
• the dielectric layer may include, for example, an oxide of a valve metal as such a material. Since the anode body includes Ta element, the dielectric layer formed by chemical conversion usually includes Ta2O5 . However, the dielectric layer is not limited to such a specific example.
• the cathode portion includes at least a solid electrolyte covering at least a portion of the dielectric layer.
• the solid electrolyte is formed in a portion on the second end side of the anode body (in other words, the cathode formation portion) via a dielectric layer.
• the cathode portion usually includes a solid electrolyte covering at least a portion of the dielectric layer, and a cathode extraction layer covering at least a portion of the solid electrolyte.
• the solid electrolyte and the cathode extraction layer will be described below.
• the solid electrolyte includes element S. Moreover, the solid electrolyte has, in an anode body having a dielectric layer, a first portion disposed within a void of a porous portion, and a second portion disposed from a main surface of the anode body having a dielectric layer to the outside of the porous portion.
• the solid electrolyte is composed of a conductive polymer.
• the conductive polymer includes a non-self-doping conductive polymer (such as a conjugated polymer and a dopant).
• the solid electrolyte may further include a self-doping conductive polymer.
• the solid electrolyte may further include an additive, if necessary.
• the S element included in the solid electrolyte is mainly derived from the conductive polymer. More specifically, the S element is included in at least the dopant, and may be included in both the dopant and the conjugated polymer.
• the S element is included in at least the first portion, and is usually included in both the first portion and the second portion.
• Part 1 At least a part of the solid electrolyte of the first portion is formed by three-electrode electrolytic polymerization as described above.
• the first portion may include a first polymer component corresponding to a conjugated polymer and a second polymer component corresponding to a polymer anion containing an S element.
• the solid electrolyte of the first portion may include a precoat layer containing a conductive polymer as a conductive material.
• Conjugated polymers corresponding to the first polymer component include known conjugated polymers used in solid electrolytic capacitors, such as ⁇ -conjugated polymers.
• Conjugated polymers corresponding to the first polymer component are usually non-self-doped conjugated polymers (e.g., conjugated polymers without anionic groups).
• Examples of such conjugated polymers include polymers having a basic skeleton of polypyrrole, polythiophene, polyaniline, polyfuran, polyacetylene, polyphenylene, polyphenylenevinylene, polyacene, and polythiophenevinylene.
• the above polymers may contain at least one monomer unit constituting the basic skeleton.
• the monomer unit also includes a monomer unit having a substituent.
• the above polymers also include homopolymers and copolymers of two or more monomers.
• polythiophenes include PEDOT (poly(3,4-ethylenedioxythiophene)).
• the first polymer component may contain an S element in order to easily increase the ratio of the S element present.
• the conjugated polymer constituting the first polymer component contains, for example, a monomer unit (preferably a repeating structure of a monomer unit) corresponding to a thiophene compound.
• a thiophene compound When a thiophene compound is used as a precursor, the electropolymerization can be easily carried out even in the presence of a polymer anion containing an S element by adjusting the electropolymerization conditions, which is more advantageous in increasing the ratio of the S element present.
• Examples of thiophene compounds include compounds that have a thiophene ring and can form a repeating structure of the corresponding monomer unit. The thiophene compound can form a repeating structure of the monomer unit by linking at the 2-position and the 5-position of the thiophene ring.
• the thiophene compound may have a substituent at least at the 3rd and 4th positions of the thiophene ring.
• the substituent at the 3rd position and the substituent at the 4th position may be linked to form a ring condensed to the thiophene ring.
• Examples of the thiophene compound include thiophenes and alkylenedioxythiophene compounds (C 2-4 alkylenedioxythiophene compounds such as ethylenedioxythiophene compounds) that may have a substituent at least at the 3rd and 4th positions.
• the alkylenedioxythiophene compound also includes a compound having a substituent in the alkylene group portion.
• substituents include, but are not limited to, alkyl groups (C 1-4 alkyl groups such as methyl and ethyl groups), alkoxy groups (C 1-4 alkoxy groups such as methoxy and ethoxy groups), hydroxy groups, hydroxyalkyl groups (hydroxy C 1-4 alkyl groups such as hydroxymethyl groups), etc.
• alkyl groups C 1-4 alkyl groups such as methyl and ethyl groups
• alkoxy groups C 1-4 alkoxy groups such as methoxy and ethoxy groups
• hydroxy groups hydroxyalkyl groups (hydroxy C 1-4 alkyl groups such as hydroxymethyl groups), etc.
• the respective substituents may be the same or different.
• a conjugated polymer such as PEDOT containing at least a monomer unit (preferably a repeating structure of monomer units) corresponding to a 3,4-ethylenedioxythiophene compound (such as 3,4-ethylenedioxythiophene (EDOT)) may be used.
• a conjugated polymer containing at least a monomer unit corresponding to EDOT may contain only a monomer unit corresponding to EDOT, or may contain, in addition to the monomer unit, a monomer unit corresponding to a thiophene compound other than EDOT.
• the weight average molecular weight (Mw) of the conjugated polymer is not particularly limited and may be, for example, 1,000 or more and 1,000,000 or less.
• the weight average molecular weight (Mw) is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC). GPC is usually measured using a polystyrene gel column and water/methanol (volume ratio 8/2) as the mobile phase.
• the first portion may contain a second polymer component corresponding to a polymer anion containing an S element as a dopant.
• a polymer anion constituting the second polymer component is a polymer having a plurality of sulfo groups.
• the polymer anion may have other anionic groups (e.g., carboxy groups) in addition to the sulfo groups.
• the anionic groups of the dopant may be contained in a free form, an anion form, or a salt form, or may be contained in a form bound to or interacting with a conjugated polymer.
• anionic groups sulfo groups, carboxy groups, etc.
• polymer anion having a sulfo group is a polymer type polysulfonic acid.
• polymer anions include polyvinyl sulfonic acid, polystyrene sulfonic acid (including copolymers and substituted products having a substituent), polyallyl sulfonic acid, polyacrylic sulfonic acid, polymethacrylic sulfonic acid, poly(2-acrylamido-2-methylpropane sulfonic acid), polyisoprene sulfonic acid, polyester sulfonic acid (such as aromatic polyester sulfonic acid), and phenolsulfonic acid novolac resin.
• the polymer anion is not limited to these specific examples.
• the solid electrolyte may contain one type of polymer anion or a combination of two or more types.
• the Mw of the polymer anion is, for example, 100 or more and 500,000 or less. Even if the weight-average molecular weight of the polymer anion is in such a range, the solid electrolyte can be arranged in the voids of the porous portion at a high filling rate by the precoat treatment and the three-electrode electrolytic polymerization, and high conductivity of the first portion is easily obtained. In addition, higher stability of the conductive polymer can be obtained. Therefore, the fluctuation of ESR when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment can be further reduced.
• the Mw of the polymer anion contained at least in the first portion is preferably 100,000 or less, more preferably 1000 or more and 100,000 or less, or more preferably 10,000 or more and 100,000 or less. Furthermore, when the Mw of the polymer anion is in such a range, higher dispersibility and a relatively high doping rate of the polymer anion are easily obtained in the first portion, which is advantageous in ensuring higher conductivity. In addition, high stability of the dopant and the conductive polymer is easily obtained.
• the amount of dopant contained in the solid electrolyte may be 10 parts by mass or more and 1000 parts by mass or less, or 20 parts by mass or more and 500 parts by mass or less, relative to 100 parts by mass of the conjugated polymer. From the viewpoint of facilitating higher dispersibility of the polymer anion and a relatively high doping rate, the amount may be 50 parts by mass or more and 200 parts by mass or less.
• the precoat layer contains, for example, a conductive material (such as a conductive polymer).
• the conductive polymer constituting the precoat layer preferably contains at least a self-doping conductive polymer, and may contain a non-self-doping conductive polymer in addition to the self-doping conductive polymer.
• the precoat layer is formed, for example, using a liquid composition (liquid dispersion, solution, etc.) containing the self-doping conductive polymer.
• the self-doping conductive polymer has, for example, a conjugated polymer skeleton and a functional group (such as an anionic group) that functions as a dopant and is directly or indirectly bonded to the skeleton by a covalent bond.
• conjugated polymers that correspond to the skeleton of the conjugated polymer include the conjugated polymers (such as ⁇ -conjugated polymers) exemplified as the conjugated polymer corresponding to the first polymer component.
• the self-doping conductive polymer is preferably a polymer having a conjugated polymer skeleton containing a repeating structure of monomer units corresponding to a thiophene compound and an anionic group introduced into the skeleton.
• the self-doped conductive polymer may have a backbone of a conjugated polymer (such as PEDOT) that contains a repeating structure of monomer units corresponding to at least a 3,4-ethylenedioxythiophene compound (such as EDOT).
• the backbone of the conjugated polymer that contains a repeating structure of monomer units corresponding to at least EDOT may contain only monomer units corresponding to EDOT, or may contain, in addition to the monomer units, monomer units corresponding to thiophene compounds other than EDOT.
• anionic groups include sulfo groups, carboxy groups, phosphate groups, and phosphonate groups.
• the self-doped conductive polymer may contain one type of anionic group, or may contain two or more types. From the viewpoint of easily ensuring higher conductivity of the self-doped conductive polymer, the self-doped conductive polymer may contain at least a sulfo group.
• the anionic group may be directly introduced into the skeleton of the conjugated polymer, or may be introduced through a linking group.
• a polyvalent group (divalent group) containing an alkylene group is preferable.
• an aliphatic polyvalent group (divalent group, etc.) such as an alkylene group, and a -R 1 -X-R 2 - group (X is an oxygen element or a sulfur element, and R 1 and R 2 are the same or different and are alkylene groups.) can be mentioned.
• the number of carbon atoms of each alkylene group contained in the linking group may be, for example, 1 or more and 10 or less, or 1 or more and 6 or less.
• the alkylene group may be linear or branched.
• the linking group may include, for example, at least an alkylene group having 2 or more carbon atoms.
• the number of carbon atoms of such an alkylene group may be 2 or more (or 3 or more) and 10 or less, or 2 or more (or 3 or more) and 6 or less.
• R 1 may be an alkylene group having 1 to 6 carbon atoms
• R 2 may be an alkylene group having 2 to 10 carbon atoms.
• the linking group is not limited to these.
• the anionic group of the self-doped conductive polymer may be present in any form, such as anion, free form, ester, or salt, or may be present in a form that interacts with or is complexed with a component contained in the first portion. In this specification, all of these forms are simply referred to as anionic groups.
• the Mw of the self-doped conductive polymer may be 1,000 or more and 1,000,000 or less, or 1,000 or more and 50,000 or less.
• the precoat layer may contain one type of self-doping conductive polymer, or a combination of two or more types.
• the capacitor element of the present disclosure at least a first peak specific to the first polymer component (conjugated polymer) and a second peak specific to the second polymer component are observed in the Raman spectrum of the first portion.
• the main component of the solid electrolyte is a conjugated polymer, and in the Raman spectrum of the solid electrolyte, the peak (first peak) attributable to the CC stretching vibration derived from the conjugated polymer is the highest and characteristic.
• the solid electrolyte exhibits high crystallinity due to the high orientation of the conjugated polymer.
• the conjugated polymer is in an energetically stabilized state. Therefore, the first portion exhibits a characteristic Raman spectrum in which the above-mentioned first and second peaks are observed.
• the Raman spectrum of the first portion observes a first peak in the range of 1200 cm -1 to 1600 cm -1 and a second peak in the range of 800 cm -1 to 1100 cm -1 .
• the second peak is attributed to the C-S stretching vibration between the aromatic ring and the S element of the sulfo group in the monomer unit corresponding to the aromatic sulfonic acid compound.
• the position of the first peak may be, for example, 1400 cm -1 to 1450 cm -1 , or 1410 cm -1 to 1435 cm -1 .
• the polymer anion contains at least polystyrene sulfonic acid
• the position of the second peak is, for example, from 900 cm ⁇ 1 to 1050 cm ⁇ 1 , and may be from 950 cm ⁇ 1 to 1050 cm ⁇ 1 .
• the Raman spectrum of the first part of the solid electrolyte formed using a liquid dispersion does not show the above-mentioned characteristic peaks. This is thought to be because the observation of Raman scattered light is hindered by the fluorescence emission.
• polymerization proceeds in the liquid phase, so it is thought that in the resulting conductive polymer particles, the high molecular weight polymer anions are more likely to segregate to the surface than in the conjugated polymer precursor.
• the conductive polymer particles with the polymer anions segregated to the surface are arranged in the porous portion, so it is thought that the above-mentioned characteristic peaks are not observed in the Raman spectrum of the first part due to the fluorescence emission from the segregated polymer anions.
• the ratio I p1 /I p2 of the intensity I p1 of the first peak specific to the first polymer component (conjugated polymer) to the intensity I p2 of the second peak specific to the second polymer component (polymer anion) may be 2 or more, 3 or more, or 4 or more.
• the ratio I p1 /I p2 is in such a range, the orientation and crystallinity of the conjugated polymer in the first portion are relatively high. Therefore, it is easy to ensure high conductivity of the solid electrolyte in the first portion.
• the ratio I p1 /I p2 may be 5 or more or 5.5 or more.
• the ratio I p1 /I p2 is, for example, 10 or less.
• the ratio I p1 /I p2 is preferably 7 or less.
• the ratio I p1 /I p2 is, for example, 2 or more and 10 or less (or 7 or less), and may be 4 or more and 10 or less (or 7 or less). In these numerical ranges, the lower limit may be replaced with the above-mentioned value. Note that the intensity of each peak corresponds to the peak height obtained by subtracting the background height from the height of each peak.
• Raman spectrometer NanoPhoton RamanFORCE PAV Diffraction grating: 600 gr/cm Measurement wave number range: 0 cm -1 or more and 2500 cm -1 or less Temperature: 25°C
• the wavelength of the irradiated laser light, the laser power density, and the exposure time are determined according to the type of the conjugated polymer. For example, when the conjugated polymer is PEDOT, the wavelength of the irradiated laser light is 784.73 nm, the laser power density is 870 W/ cm2 , and the exposure time is 60 seconds.
• the solid electrolytic capacitor or capacitor element is embedded in a curable resin, and the curable resin is cured.
• the cured product is polished or cross-section polished to expose a cross section perpendicular to the length direction of the capacitor element and parallel to the thickness direction.
• the cross section is located at a position greater than 0 and less than 0.05 from the end (end on the second end side) of the region where the solid electrolyte is formed on the opposite side to the anode lead-out portion, where the length of the region where the solid electrolyte is formed in the direction parallel to the length direction of the capacitor element is 1. In this way, a sample for measurement is obtained.
• the Raman spectrum is measured for an 8 ⁇ m x 8 ⁇ m region of the solid electrolyte (first portion) formed in the pits on the surface of the porous portion.
• the intensities of the first and second peaks are obtained by averaging the measured values for 12 8 ⁇ m x 8 ⁇ m regions of the first portion formed in the pits of the porous portion.
• At least the first part of the solid electrolyte can be formed by precoating the surface of the dielectric layer, and then electrolytically polymerizing the precursor of the conjugated polymer in the presence of a dopant in a three-electrode manner.
• the anode body having the dielectric layer is precoated with a liquid composition (polymerization liquid) containing the precursor of the conjugated polymer and the dopant, and then electrolytic polymerization is performed while the cathode forming portion of the anode body is immersed.
• the solid electrolyte By adjusting the conditions of the precoating process and the conditions of the electrolytic polymerization, the solid electrolyte can be arranged at a high filling rate in the fine voids of the porous portion of the anode body containing the Ta element, and the abundance ratio of the S element can be increased.
• the dopant can be doped at a relatively high doping rate, and the high conductivity of the solid electrolyte can be ensured, and the conjugated polymer can be energetically stabilized. Therefore, the deterioration of the solid electrolyte when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment can be suppressed, and the high conductivity can be maintained, so that the fluctuation of the ESR can be reduced.
• Conjugated polymer precursors include raw material monomers for conjugated polymers, and oligomers and prepolymers in which multiple molecular chains of raw material monomers are linked together.
• One type of precursor may be used, or two or more types may be used in combination. From the viewpoint of facilitating the achievement of higher orientation of the conjugated polymer, it is preferable to use at least one type (particularly a monomer) selected from the group consisting of monomers and oligomers as the precursor.
• Liquid compositions usually contain a solvent.
• the solvent include water, an organic solvent, and a mixture of water and an organic solvent (such as a water-soluble organic solvent).
• the liquid composition may contain an oxidizing agent as necessary.
• the oxidizing agent may be applied to the anode body before or after contacting the liquid composition with the anode body on which the dielectric layer is formed.
• examples of such oxidizing agents include compounds capable of generating Fe3 + (such as ferric sulfate), persulfates (such as sodium persulfate and ammonium persulfate), and hydrogen peroxide.
• the oxidizing agents may be used alone or in combination of two or more.
• the three-electrode electrolytic polymerization is carried out in a state where an anode body, a counter electrode, and a reference electrode are immersed in the liquid composition.
• the counter electrode may be, but is not limited to, a Ti electrode.
• the reference electrode is preferably a silver/silver chloride electrode (Ag/Ag + ).
• the voltage (polymerization voltage) applied to the anode body is, for example, 0.6 V or more and 1.5 V or less.
• the polymerization voltage is preferably more than 0.9 V and 1.2 V or less (or 1.1 V or less), and may be 1.0 V or more and 1.2 V or less, or 1.0 V or more and 1.1 V or less.
• the polymer chains of the conjugated polymer can be grown in a state in which the dopant is highly dispersed, and the solid electrolyte can be placed in the voids at a high filling rate.
• the polymerization can be allowed to proceed slowly, the orientation and crystallinity of the conjugated polymer can be further increased, a relatively high doping rate can be obtained, and a relatively high conductivity can be easily secured.
• the polymerization voltage is the potential of the anode body relative to a reference electrode (silver/silver chloride electrode (Ag/Ag + )).
• the temperature at which electrolytic polymerization is performed is, for example, 5°C or higher and 60°C or lower, and may be 15°C or higher and 35°C or lower.
• the surface of the dielectric layer Prior to electrolytic polymerization, the surface of the dielectric layer is precoated.
• the precoating is performed, for example, using a conductive material (such as a conductive polymer).
• the precoating may be performed using either a self-doping conductive polymer or a non-self-doping conductive polymer.
• the precoating may be performed using a liquid composition (such as a liquid dispersion or solution) that contains at least a self-doping conductive polymer.
• the liquid dispersion used for the precoat process has a smaller conductive polymer particle size and a lower concentration than the liquid dispersion used to form the solid electrolyte constituting the cathode.
• the average primary particle size of the conductive polymer particles contained in the liquid dispersion for the precoat process may be 100 nm or less, or may be 60 nm or less.
• the dry solid content concentration of the liquid dispersion is, for example, 1.2 mass% or less.
• the average primary particle size of the conductive polymer particles is usually 200 nm or more, and the dry solid content concentration is 2 mass% or more.
• the conjugated polymer used for the precoat process (or the conjugated polymer forming the skeleton of the self-doped conductive polymer) and the conjugated polymer formed by electrolytic polymerization may be the same type or different types.
• the dopant used for the precoat process and the dopant used for electrolytic polymerization may be the same or different.
• the precoat treatment is performed by applying a liquid composition containing a conductive material (such as a conductive polymer) to an anode body (specifically, a cathode forming portion) having a dielectric layer and drying it. It is preferable to repeat the application and drying of the liquid composition two or more times. Even if the anode body is a porous molded body or a porous sintered body, the coverage rate of the precoat layer on the surface, including the inner walls of the voids in the porous portion, can be increased by repeating the application and drying of the liquid composition multiple times.
• a conductive material such as a conductive polymer
• a more uniform and dense solid electrolyte can be formed with a high filling rate by electrolytic polymerization, making it easier to ensure high stability and high conductivity of the first portion.
• the formation of the first portion with a high filling rate in the voids reduces air circulation. As a result, deterioration of the solid electrolyte in the first portion when the solid electrolytic capacitor is exposed to a high temperature or high temperature and high humidity environment is suppressed, and the fluctuation of ESR can be reduced.
• the second part may be configured as a layer (solid electrolyte layer) as a whole.
• the second part may be different from the first part in at least one of the composition of the solid electrolyte and the film quality, or may be the same in both the composition and the film quality.
• the second part may be configured of a plurality of layers. At least two layers of the plurality of layers may be different in at least one of the composition and the film quality, or may be the same in both.
• the solid electrolyte of the second portion may be formed by chemical polymerization, general two-electrode electrolytic polymerization, or using a liquid dispersion, but it is preferable to form the second portion by three-electrode electrolytic polymerization, from the viewpoint that the dopant is highly dispersed throughout the solid electrolyte, high conductivity is easily ensured, and degradation of the solid electrolyte is easily suppressed.
• the conjugated polymer contained in the second part may be selected from the conjugated polymers described for the first part, for example.
• the Mw of the conjugated polymer may be selected from the range described for the first part.
• the dopant at least one selected from the group consisting of the polymer anions and anions described for the first part may be used.
• the anions include, but are not limited to, sulfate ions, nitrate ions, phosphate ions, borate ions, organic sulfonate ions, and carboxylate ions.
• dopants that generate sulfonate ions include p-toluenesulfonic acid and naphthalenesulfonic acid. From the viewpoint of obtaining higher stability, it is preferable to use a polymer anion.
• the amount of dopant contained in the solid electrolyte may be, for example, 10 parts by mass or more and 1,000 parts by mass or less, 20 parts by mass or more and 500 parts by mass or less, or 50 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the conjugated polymer.
• the second part may be formed using a liquid dispersion (or solution) containing a conjugated polymer and a dopant.
• the second part may be formed in the same manner as described for the first part.
• the polymerization voltage for electrolytic polymerization may be in the range described for the first part, and may be 0.6 V or more and 1.5 V or less, or 0.7 V or more and 1.2 V or less.
• Each of the first and second parts may further contain at least one selected from the group consisting of known additives and known conductive materials other than conductive polymers, for example, at least one selected from the group consisting of conductive inorganic materials such as manganese dioxide and TCNQ complex salts.
• Additives include known additives added to solid electrolytes (e.g., coupling agents, silane compounds), known conductive materials other than conductive polymers, and water-soluble polymers.
• Each of the first and second parts may contain one type of these additives, or may contain a combination of two or more types. When each part is composed of multiple layers, the additives contained in each layer may be the same or different.
• Each of the first and second parts may be a single layer or may be composed of multiple layers.
• the types, compositions, and contents of the conductive polymers, additives, etc. contained in each layer may be the same or different.
• a layer that enhances adhesion may be interposed between the dielectric layer and the solid electrolyte.
• the solid electrolytes constituting the first or second part can be distinguished, for example, by electron probe microanalyzer (EPMA) analysis of a cross-sectional image.
• EPMA analysis can be performed at equal intervals on a cross-sectional image of the entire solid electrolyte layer, and the interface between adjacent solid electrolytes can be determined from the difference in wavelength of characteristic X-rays at each measurement point.
• the measurement sample is prepared in the same manner as the sample for Raman spectrum measurement.
• the cathode extraction layer may include at least a first layer that is in contact with the solid electrolyte and covers at least a part of the solid electrolyte, and may include the first layer and a second layer that covers the first layer.
• the first layer include a layer containing conductive particles and a metal foil.
• the conductive particles include at least one selected from conductive carbon and metal powder.
• the cathode extraction layer may be composed of a layer containing conductive carbon (also referred to as a carbon layer) as the first layer and a layer containing metal powder or a metal foil as the second layer. When a metal foil is used as the first layer, the cathode extraction layer may be composed of this metal foil.
• Examples of conductive carbon include graphite (artificial graphite, natural graphite, etc.).
• the layer containing metal powder as the second layer can be formed, for example, by laminating a composition containing metal powder onto the surface of the first layer.
• a composition containing metal powder such as silver particles and a resin (binder resin).
• a thermoplastic resin can be used as the resin, it is preferable to use a thermosetting resin such as an imide resin or an epoxy resin.
• the type of metal is not particularly limited. It is preferable to use a valve metal (aluminum, tantalum, niobium, etc.) or an alloy containing a valve metal for the metal foil. If necessary, the surface of the metal foil may be roughened. The surface of the metal foil may be provided with a chemical conversion coating, or may be provided with a coating of a metal (heterogeneous metal) different from the metal constituting the metal foil or a nonmetal. Examples of heterogeneous metals and nonmetals include metals such as titanium and nonmetals such as carbon (conductive carbon, etc.).
• the coating of the dissimilar metal or nonmetal may be the first layer, and the metal foil may be the second layer.
• the solid electrolytic capacitor includes at least one capacitor element.
• the solid electrolytic capacitor may be of a wound type, and may be either a chip type or a stacked type.
• the solid electrolytic capacitor may include a plurality of stacked capacitor elements.
• the solid electrolytic capacitor may also include two or more wound capacitor elements. The configuration of the capacitor element may be selected according to the type of the solid electrolytic capacitor.
• one end of the cathode lead terminal may be electrically connected to the cathode lead layer.
• the cathode lead terminal is bonded to the cathode lead layer via the conductive adhesive, for example, by applying a conductive adhesive to the cathode lead layer.
• One end of the anode lead terminal may be electrically connected to the anode lead portion of the anode body.
• the other end of the anode lead terminal and the other end of the cathode lead terminal are each drawn out from the resin exterior body or case.
• the other end of each terminal exposed from the resin exterior body or case is used for solder connection with the substrate on which the solid electrolytic capacitor is to be mounted.
• at least one end face of the anode portion and the cathode portion may be exposed from the outer surface of the sealing body and electrically connected to an external electrode.
• the capacitor element is sealed using a resin exterior body or case.
• the capacitor element and the resin material of the exterior body e.g., uncured thermosetting resin and filler
• the capacitor element and the resin material of the exterior body may be placed in a mold, and the capacitor element may be sealed in the resin exterior body by transfer molding, compression molding, or the like.
• the other end sides of the anode lead terminal and the cathode lead terminal connected to the anode lead drawn out from the capacitor element are exposed from the mold.
• the capacitor element may be placed in a bottomed case such that the other end sides of the anode lead terminal and the cathode lead terminal are positioned on the opening side of the bottomed case, and the opening of the bottomed case may be sealed with a sealant to form a solid electrolytic capacitor.
• the leads may be wire-shaped or frame-shaped (such as a lead frame).
• FIG. 1 is a schematic cross-sectional view of a solid electrolytic capacitor according to one embodiment of the present disclosure.
• the solid electrolytic capacitor 20 includes a capacitor element 10 including an anode portion 6 and a cathode portion 7, an exterior body 11 that seals the capacitor element 10, an anode lead frame 13 electrically connected to the anode portion 6, and a cathode lead frame 14 electrically connected to the cathode portion 7.
• the anode section 6 has an anode body 1 and an anode wire 2.
• a part of the anode wire 2 is embedded in the anode body 1, and the remainder protrudes outward from the outer surface of the anode body 1.
• a part of the first part of the anode lead frame 13 is joined to the protruding part of the anode wire 2 by welding or the like, and is electrically connected.
• a dielectric layer 3 is formed on the surface of the anode body 1.
• the cathode section 7 has a solid electrolyte layer 4 covering at least a portion of the dielectric layer 3, and a cathode lead layer 5 covering at least a portion of the surface of the solid electrolyte layer 4.
• the cathode lead layer 5 has a carbon layer formed so as to cover at least a portion of the surface of the solid electrolyte layer 4, and a metal particle-containing layer formed so as to cover at least a portion of the carbon layer.
• a portion of the first portion of the cathode lead frame 14 is adhered to the cathode lead layer 5 via the conductive adhesive layer 8, and is electrically connected thereto.
• Examples 1 and 2 and Comparative Example 1 A capacitor element was produced in the following manner, and its characteristics were evaluated.
• anode body having a dielectric layer A tantalum sintered body (porous body) in which a part of an anode wire was embedded was prepared as an anode body. This tantalum sintered body was immersed in a chemical conversion solution, and a direct current voltage of 70 V was applied for 20 minutes to perform anodization. In this way, a dielectric layer containing tantalum oxide was formed on the surface of the anode body.
• Electrochemical polymerization 3,4-ethylenedioxythiophene monomer and polystyrene sulfonic acid (PSS, Mw: 100,000) which is a polymer anion were dissolved in ion-exchanged water to prepare a mixed solution.
• Iron (III) sulfate (oxidant) dissolved in ion-exchanged water was added while stirring the mixed solution to prepare a polymerization solution.
• Electrochemical polymerization was performed in a three-electrode system using the obtained polymerization solution. More specifically, an anode body on which a precoat layer was formed, a counter electrode, and a reference electrode (silver/silver chloride reference electrode) were immersed in the polymerization solution. A voltage was applied to the anode body so that the potential of the anode body relative to the reference electrode was 1.1 V, and electrochemical polymerization was performed at 25 ° C.
• a silver paste containing silver particles and binder resin epoxy resin
• the binder resin was cured by heating at 150-200°C for 10-60 minutes to form the second layer (metal particle-containing layer).
• a cathode lead layer composed of the first layer (carbon layer) and the second layer (metal particle-containing layer) was formed, and a cathode part composed of the solid electrolyte layer and cathode lead layer was formed.
• Example 1 A solid electrolyte layer was formed in the following manner.
• a capacitor element was fabricated in the same manner as in Example 1 except for the above.
• a polymerization solution containing pyrrole (monomer of conjugated polymer), naphthalenesulfonic acid (dopant), and distilled water was prepared.
• the obtained polymerization solution was used to carry out electrolytic polymerization in a three-electrode system. More specifically, the anode body on which the precoat layer was formed, a counter electrode, and a reference electrode (silver/silver chloride reference electrode) were immersed in the polymerization solution.
• a voltage was applied to the anode body so that the potential of the anode body relative to the reference electrode was 0.9 V, and electrolytic polymerization was carried out at 25°C to form a solid electrolyte layer.
• the concentration of pyrrole in the polymerization solution was approximately 1.3 mass%, and the concentration of the dopant was approximately 4 mass%.
• the ESR (m ⁇ ) of the capacitor elements after cooling was measured under the same conditions as for the initial ESR measurement, and the average value (R1) of the 10 elements was calculated.
• the ESR variation 1 (m ⁇ ) was calculated by subtracting R0 from R1.
• the remaining 10 capacitor elements were left in an environment of 85°C and 85% RH for 600 hours, and then cooled to 20°C.
• the ESR (m ⁇ ) of the capacitor elements after cooling was measured under the same conditions as the initial ESR measurement, and the average value (R2) of the 10 elements was calculated.
• the ESR variation 2 (m ⁇ ) was calculated by subtracting R0 from R2.
• Capacitor elements E1 and E2 are Examples 1 and 2
• capacitor element C1 is Comparative Example 1
• capacitor element R1 is Reference Example 1.
• ESR fluctuations 1 and 2 are shown as relative values when the fluctuation in Comparative Example 1 is set to 1.00.
• capacitor element R1 As shown in Table 1, in a capacitor element in which the solid electrolyte layer is formed by electrolytic polymerization of pyrrole, the amount of ESR fluctuation when exposed to high temperatures (or high temperature and high humidity environment) is very large (capacitor element R1). In capacitor element C1, in which the abundance ratio of S element in the first part is less than 0.17%, the amount of ESR fluctuation is reduced compared to capacitor element R1, but the amount of fluctuation is still large. In contrast, in the examples (capacitor elements E1 to E2) in which the abundance ratio of S element in the first part is 0.17% or more, the amount of ESR fluctuation is significantly reduced, and it can be seen that excellent reliability is obtained.
• the abundance ratio of S element in the first part is lower than 0.14% of capacitor element C1, and the amount of ESR fluctuation 1 and 2 are larger than that of capacitor element C1.
• the capacitor element and solid electrolytic capacitor of the present disclosure can ensure a stable, low ESR even when exposed to high temperatures (or a high-temperature, high-humidity environment), and therefore can be used in a variety of applications requiring heat resistance, moisture resistance, or reliability.
• the applications of the capacitor element and solid electrolytic capacitor are not limited to these.
• Solid electrolytic capacitor 10 Capacitor element 1: Anode body 2: Anode wire 3: Dielectric layer 4: Solid electrolyte layer 5: Cathode lead layer 6: Anode portion 7: Cathode portion 8: Conductive adhesive layer 11: Exterior body 13: Anode lead frame 14: Cathode lead frame

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